Stents and other implantable medical devices which incorporate stents are in widespread use in the medical field for dilating patient's vessels, for closing off aneurysms, for treating vascular dissections, for supporting prosthetic elements and so on. Stents have the function of holding the vessel open or for holding a device securely against the vessel wall to effect a good seal as well as to prevent device migration. As a result, it is desirable for the stent to be able to apply a significant opening force and to do so reliably. However, in many instances it is undesirable to maintain pressure against the vessel wall for prolonged periods of time. Long term pressure applied to the vessel wall can cause undesired long term effects such as unnecessary stretching or straightening of the vessel. It is also, in some instances, undesirable to retain long term in a patient's body significant amounts of metal or alloy. These effects can lead to vessel weakening of the vessel and/or stenosis or restenosis.
It is generally undesirable to remove the stent or other medical device from a patient by means of an invasive medical procedure. Attempts have been made, thus, to produce stents which are biodegradable or bioresorbable. While such stents can resolve the problems encountered during the long term use of such implantable medical devices, biodegradable or bioresorbable stents do not generally have the same performance characteristics as stents made purely of metal or metal alloy, resulting in potential loss of efficacy.
Disclosures of biodegradable and bioabsorbable stents can be found, for example, in: US-2005/0163822, U.S. Pat. No. 7,594,928, US-2006/0052863, U.S. Pat. No. 7,879,367, US-2007/0250155, US-2006/0193891, US-2007/0203564, U.S. Pat. Nos. 7,279,005 and 5,980,564.